<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>4.3 10！</title>
</head>

<body>
    <script>
        var fac = 1;
        for (var i = 1; i <= 10; i++) {
            fac *= i;
        }
        alert('10!=' + fac)
    </script>
</body>

</html>